.box{
    margin: 50px 200px;
}
.img {
    width: 300px;
    height: 300px;
    position: relative;
    background: url('./imgs/3.jpg');
    display: inline-block;

}

.mask {
    width: 100px;
    height: 100px;
    background-color: yellow;
    opacity: .5;
    position: absolute;
    left: 0px;
    top: 0px;
    visibility:hidden;
}

.enlarge {
    width: 200px;
    height: 200px;
    background: url('./imgs/6.jpg');
    background-position: 0px 0px;
    display: inline-block;
    visibility:hidden;

}